Where is Cost Derived When Doing Goods Receipt

Explan what are the cost account when doing the goods receipt. For example when doing GR, system post as follows.

Dr Stock (is this the cost of sales?)
Cr GR/IR (what exactly is GR/IR)

and when do IV it post

Dr GR/IR
Cr Vendor etc.

Goods Receipts/Invoice Receipts for Purchase Order:
Transaction OMW1 allows you to set whether the Price Control is a mandatory "S" or "V".
- V indicate that you want the system to value the stocks with the latest price.
- S indicate that you want the system to value the stocks with a fixed price method.

Price Control V - Moving Average Price
Assume Material Master current price is 10
Goods Receipts for Purchase Order - Movement Type 101
Material Document Posting created - inventory increases

Accounting Document Posting created
Debit 12345 Inventory 12
Credit 67890 GR/IR 12

New Moving Average Price = ( GR value + Total value ) / ( GR quantity + Total stock )

Invoice Recipts for Purchase Order - MR01

Accounting Document Posting created
Debit 67890 GR/IR 12
Debit 12345 Inventory 3
Credit 45678 Vendor 15

New Moving Average Price = ( Inventory difference of 2 + Total value ) / ( Total Stock)

Price Control S - Standard Price
Material and Accounting Document is the same.
The one with the lower value will be posted with a price variance entry.

Goods Receipts for Purchase Order - Movement Type 101
Material Document Posting created - inventory increases

Accounting Document Posting created
Debit 12345 Inventory 10
Debit 23456 Price Variance 2
Credit 67890 GR/IR 12

No change in Standard Price

Invoice Recipts for Purchase Order - MR01

Accounting Document Posting created
Debit 67890 GR/IR 12
Debit 23456 Price Variance 3
Credit 45678 Vendor 15

No change in Standard Price